HLA

HLA or Human Leukocyte Antigen is a complex genetic system located on chromosome 6. It plays a crucial role in immune response. HLA genes are highly polymorphic, which means they have many different alleles, allowing them to fine-tune the immune system.

Overview

The HLA system is the human version of the major histocompatibility complex (MHC), which is found in all vertebrates. The HLA genes are grouped in three categories: HLA Class I, HLA Class II, and HLA Class III.

• HLA Class I molecules are found on all nucleated cells and platelets. They present endogenous antigens to cytotoxic T cells.
• HLA Class II molecules are found on antigen-presenting cells (APCs), including macrophages, dendritic cells, and B cells. They present exogenous antigens to helper T cells.
• HLA Class III genes encode components of the complement system.

Function

HLA molecules bind peptide fragments derived from pathogens and display them on the cell surface for recognition by the appropriate T-cells. This process is crucial for immune response.

Clinical significance

HLA genes have been linked to a number of diseases, including autoimmune diseases, infectious diseases, and cancer. HLA typing, which identifies HLA alleles in an individual, is used in organ transplantation to predict the compatibility of donor and recipient.

See also

• Major histocompatibility complex
• Antigen-presenting cell
• T cell
• Autoimmune disease
• Organ transplantation

References

HLA Resources
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